A unique set of circumstances access to the resources of Independent School District #535 Student Support Services (which provides evaluation and management for the children from all public, parochial, and private schools in Rochester), of the privately owned Rochester Reading Center (which includes a pool of some 3,000 evaluations and outcomes of tutorial instruction that span nearly 50 years), and of the established Rochester Epidemiology Project (a richly-documented medical records-linkage system located at Mayo Clinic) -- will enable us to conduct a number of studies to further our knowledge of learning disabilities (LD) in a delineated population. For this study, LD will include dyslexia and problems related to writing, reasoning, and mathematics. These entities have long been recognized for their significant social, educational, and medical import. This study will produce estimates of the incidence of LD among a birth cohort of children, born 1976-1980 in Rochester, Minnesota, as well as to determine the prevalence of LD on August 1, 1992. Further, a nested case-control study will assess the association between factors from birth certificates and medical records, as well as a parent questionnaire, with risk of developing LD. We will estimate the amount of familial aggregation of LD and we will determine the genetic and non- genetic components that influenced any observed familial aggregation. Also, complex segregation analysis will be conducted with learning disabled incident cases as probands. We will assess the potential impact of referral biases inherent in referral-based studies of LD by comparing the population-based incident learning disabled cases with learning disabled cases (born during the same period of time) from the Mayo referral practice. Finally, the current status of incident cases, 1976- 1980, and their matched controls will be assessed using a group of standard psychological tests for each student to better understand the long-term outcomes of children with LD. Thus, at the conclusion of this study, we will have advanced our knowledge of the occurrence of LD, and provided new information about the etiology and familial aggregation of LD and further insight of the natural history/clinical course of the disorder.